EVs and Brake Lights

youtheman

Do the Brake Lights on an EV come on when they are ‘regenerative braking’. I’ve noticed lately that when I’m driving behind an EV on a wide open road their brake lights come on intermittently and for no apparent reason. Can be quite disconcerting !. I initially though the driver must be drunk !. Then I thought maybe this is happening automatically when the car is in cruise control.

On a normal ICE the cruise control can only adjust you acceleration. But if you have it set and you end up going down a hill then the car can exceed the speed you have set. But maybe an EV can actually stop over-speeding by automatically applying the brakes. Anyone able to confirm this?

ELM327

https://www.boards.ie/discussion/2058383525/evs-and-brake-lights

Yes. EV and hybrids apply brake lights once regen over a certain amount of G is detected.

Same happens when on autopilot. Regen applies the brake lights when going down a steep enough hill.

Allinall

I've wondered the same with cars that have adaptive cruise control.

Had one as a rental recently, and a couple of times it slowed fairly quickly coming up to traffic congestion, and was wondering about the brake lights warning those coming up behind.

GSBellew

https://www.boards.ie/discussion/2058383525/evs-and-brake-lights

Could just be a brake happy driver, you do see them in all manner of vehicle.

As for the question, yes brake lights come on under regen, they also do with adaptive cruise control or active brake assist etc.

DaveyDave

https://www.boards.ie/discussion/comment/122929396#Comment_122929396

In my experience yes, ACC will activate the brakes once over a certain amount of force.

Varik

The EU law changed at the start of 2023 to deal properly with regenerative breaking but before that there was a stupid exception. The US mandated when you need it, and then left the manufactures choose when else it could come one but the EU actually barred it at one particular time with regenerative.

It used to be that the light was required when hitting the actual brakes (obv), in one pedal modes and in cruise control automatic modes above 0.7m/s3 . But they actually barred it in 2 pedal normal modes with regenerative braking.

Now it's above 1.3m/s3 its required and below that it may be used.

BobMc

what about one pedal driving, you can come to a nearly a full stop with no brakes often wondered are brake lights working when using one pedal driving?

AndyBoBandy

https://www.boards.ie/discussion/comment/122942268#Comment_122942268

yes, they are. and will remain on when the car is in 'hold' with no force applied to any pedal

liamog

https://www.boards.ie/discussion/comment/122942279#Comment_122942279

It depends on model, there's no standard for what a car must do when in a holding position. My Mini used to leave the brake lights off when stopped waiting at lights.

BobMc

knew they stayed on for Hold alright, so once you lift foot from accelarator pedal brake lights come on ? its the missus in the EV and wondered

SodiumCooled

https://www.boards.ie/discussion/2058383525/evs-and-brake-lights

Any ICE car with adaptive adaptive cruise control (which is very common now especially with VW and Skoda having it as standard on most models) will apply the brakes also - it will take you to a complete stop in-fact and you can drive in traffic using it (especially with an auto).

creedp

https://www.boards.ie/discussion/comment/122942279#Comment_122942279

That'll upset a few people. It's not that long ago I was reading a thread where people were complaining about being blinded by drivers keeping their foot on the brake at traffic lights. Looks like they may just have to wear shades😃

User1998

https://www.boards.ie/discussion/comment/122942500#Comment_122942500

Yeah, Tesla definitely keeps the brake lights on when using auto hold, but I know a VW Golf does not. It can be quite annoying being stuck behind a car in traffic with its brake lights on

cnocbui

https://www.boards.ie/discussion/comment/122942650#Comment_122942650

I'd find a car with no brake light that rolled back and hit mine, to be more annoying.

User1998

https://www.boards.ie/discussion/comment/122942740#Comment_122942740

Right, but there are plenty of cars that have autohold and don’t keep the brake light on constantly

kirving

Mercedes for example can dim the brake lights in traffic so as not to dazzle drivers behind.

https://youtu.be/dRKrZW6yX14?t=142

My E-Class would not allow me to flash the brake lights quickly, it was computer controlled so that the minimum ON time of the brake lights was always 1 second or so. I thought that was a good idea in theory, but I much preferred the Volvo concept of linking the brake lights to the pedal, even if the car was off. Even if the engine was dead, the car wouldn't start, pressing the pedal would still illuminate the brake lights (horn would work too).

https://www.boards.ie/discussion/comment/122934301#Comment_122934301

There's a fine line between constantly, unnecessarily flashing drivers behind, to the point that they ignore brake lights and illuminating them when necessary. In just 10s, at -1.3m/s^2 you'll slow by almost 50km/h.

The below video is an interesting explanation (from a great channel) on the unintended consequences of manufactures following the regulations to the letter. Asian manufacturers in general, have terrible implementations of lighting control, dangerously so in many cases IMO.

https://www.youtube.com/watch?v=U0YW7x9U5TQ

Gumbo

https://www.boards.ie/discussion/comment/122942294#Comment_122942294

BMw and Tesla will do the same, lights on when on H. Seems to be the same across the board.

Edit. Thought the mine remained on, hence agreeing with the post.

creedp

https://www.boards.ie/discussion/comment/122944098#Comment_122944098

Are you sure that's the position with Model 3? I kept an eye on the high level brake light this evening (can just see the illumination at base of rear screen in the dark) when stopping using accelerator pedal only and noticed it remained illuminated for the time I was stopped at lights.

Gumbo

https://www.boards.ie/discussion/comment/122944464#Comment_122944464

Sorry my error, I misread it as the mini keeps the lights on rather than off.

liamog

I enjoyed the brake light being off, was great looking back in the mirror at the drivers who hadn't copped you moved off when the lights went green. A surprising number of drivers looking down into their laps for some reason, I wonder what it could have been?

Vestiapx

https://www.boards.ie/discussion/comment/122944057#Comment_122944057

One of my favorite channels and quite passio ate in his own way about EV tech (and heat pumps)

Gumbo

https://www.boards.ie/discussion/comment/122944592#Comment_122944592

Playing with themselves 👀